Message ID | 20221102183336.3120536-6-vschneid@redhat.com |
---|---|
State | New |
Headers | show
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McKenney" <paulmck@kernel.org>, Steven Rostedt <rostedt@goodmis.org>, Peter Zijlstra <peterz@infradead.org>, Thomas Gleixner <tglx@linutronix.de>, Sebastian Andrzej Siewior <bigeasy@linutronix.de>, Juri Lelli <juri.lelli@redhat.com>, Daniel Bristot de Oliveira <bristot@redhat.com>, Marcelo Tosatti <mtosatti@redhat.com>, Frederic Weisbecker <frederic@kernel.org>, Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>, Dave Hansen <dave.hansen@linux.intel.com>, "H. Peter Anvin" <hpa@zytor.com>, Marc Zyngier <maz@kernel.org>, Mark Rutland <mark.rutland@arm.com>, Russell King <linux@armlinux.org.uk>, Nicholas Piggin <npiggin@gmail.com>, Guo Ren <guoren@kernel.org>, "David S. Miller" <davem@davemloft.net> Subject: [RFC PATCH v2 7/8] smp: reword smp call IPI comment Date: Wed, 2 Nov 2022 18:33:35 +0000 Message-Id: <20221102183336.3120536-6-vschneid@redhat.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20221102182949.3119584-1-vschneid@redhat.com> References: <20221102182949.3119584-1-vschneid@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-3.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: <sparclinux.vger.kernel.org> X-Mailing-List: sparclinux@vger.kernel.org |
Series |
Generic IPI sending tracepoint
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expand
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diff --git a/kernel/smp.c b/kernel/smp.c index 44fa4b9b1f46b..b96579fe08f09 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -503,9 +503,10 @@ void __smp_call_single_queue(int cpu, struct llist_node *node) #endif /* - * The list addition should be visible before sending the IPI - * handler locks the list to pull the entry off it because of - * normal cache coherency rules implied by spinlocks. + * The list addition should be visible to the target CPU when it pops + * the head of the list to pull the entry off it in the IPI handler + * because of normal cache coherency rules implied by the underlying + * llist ops. * * If IPIs can go out of order to the cache coherency protocol * in an architecture, sufficient synchronisation should be added
Accessing the call_single_queue hasn't involved a spinlock since 2014: 6897fc22ea01 ("kernel: use lockless list for smp_call_function_single") The llist operations (namely cmpxchg() and xchg()) provide similar ordering guarantees, update the comment to lessen confusion. Signed-off-by: Valentin Schneider <vschneid@redhat.com> --- kernel/smp.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)